Historically, internal combustion engines have employed electric fuel pumps to pump fuel from a fuel tank of a motor vehicle to a fuel rail of the internal combustion engine. The fuel rail is used to distribute the fuel to a plurality of fuel injectors which in turn inject the fuel into an air intake manifold of the internal combustion where the fuel is mixed with air prior to being ingested into combustion chambers of the internal combustion engine through respective intake valves. Fuel injection systems where the fuel injectors inject the fuel into the air intake manifold are commonly referred to as port fuel injection systems. In port fuel injection systems, the electric fuel pump alone is sufficient to supply fuel at a pressure needed at the fuel injectors where the pressure is typically below 500 kPA. However, direct injection fuel injection systems have become increasingly common in an effort to maximize fuel economy and to minimize harmful emissions produced by the internal combustion engine. In direct injection fuel injection systems, the fuel injectors inject fuel directly into respective combustion chambers under high pressure where the fuel typically needs to be supplied at a pressure above 14 MPa. Since the electric fuel pump is not able to accommodate this magnitude of pressure, the electric fuel pump supplies fuel at low pressure to a high-pressure fuel pump which is typically in the form of a reciprocating plunger driven by a cam lobe of the internal combustion engine. The high-pressure fuel pump includes an electrically actuated intake or spill valve which allows fuel to enter a pressure chamber during the intake stroke of the plunger. During the pressure stroke of the plunger, the spill valve is closed, thereby allowing the plunger to decrease the volume of the pressure chamber, consequently pressurizing the fuel. When the fuel reaches a predetermined pressure, an outlet valve is opened under the force of the pressurized fuel and the fuel is communicated to the fuel rail and fuel injectors. In order to vary the pressure generated by the high-pressure fuel pump, the spill valve can be commanded to remain open for a portion of the compression stroke of the plunger, thereby decreasing the fuel pressure generated by the high-pressure fuel pump in order to accommodate different operating conditions of the internal combustion engine. However, when the spill valve remains open during a portion of the compression stroke of the plunger, pressure pulsations generated by the plunger can propagate upstream of the spill valve which can have undesirable effects on the electric fuel pump and other components in the fuel system. Consequently, these pressure pulsations need to be attenuated.
An example of a high-pressure fuel pump is shown in U.S. Pat. No. 8,430,081 to Mancini et al. on Apr. 30, 2013. In this example, the pressure pulsations are attenuated by a pair of pulsation dampers which are disposed within a fluid volume that is exposed to the pressure pulsations. Each pulsation damper includes first and second halves which define a sealed damping volume such that the first and second halves each include a damper wall that is configured to flex in response to the pressure pulsations, thereby decreasing the damping volume and attenuating the pressure pulsations. In order to allow the damper walls to flex in response to the pressure pulsations, it is important that the damper walls be exposed to the fuel within fluid volume. Consequently, the arrangement of U.S. Pat. No. 8,430,081 provides spacers between the pulsation dampers and also between each pulsation damper and the wall which defines the fluid volume in order to support the pulsation dampers, thereby suspending the damper walls within the fluid volume. As a result the arrangement of U.S. Pat. No. 8,430,081 requires many pieces that must be assembled, thereby requiring a great deal of packaging space and adding cost and complexity in the manufacturing process.
International Publication No. WO 2015/011545 A1 to Yabuuchi et al. on Jan. 29, 2015 shows another pulsation damper arrangement for high-pressure fuel pumps. In the arrangement of WO 2015/011545 A1, the pulsation dampers are a three-piece assembly comprising a first diaphragm and a second diaphragm separated by an attachment member. The attachment member includes a plurality of protrusions that extend radially outward and engage a complementary retention groove formed on the inner surface of the wall which defines the fluid volume. While the pulsation damper of WO 2015/011545 A1 is self-supporting, the attachment member adds an extra part, and consequently an extra weld, to the pulsation damper compared to U.S. Pat. No. 8,430,081. Furthermore, the pulsation damper of WO 2015/011545 A1 requires a retention groove to be formed on the inner surface of the wall which defines the fluid volume, thereby adding cost and complexity in manufacturing. A risk of the pulsation damper coming out of the retention groove in use also exists which could render the pulsation damper ineffective.
What is needed is a pulsation damper which minimizes or eliminates one or more of the shortcomings as set forth above.